Expulsion fuse



1 all cost.

Patented Jul; 5, 1927.

UNITED" srarss PATENT OFFICE.

RICHARD 3. HUGE, OI BLLLS'ION 14m, raw YORK, LASSIGNOi '10 GENERAL ELEC- 231d OOIPAII'Y ,,A CORPORATION 01' NEW YORK.

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The safety potential enclosed fuses o y a The ob ect of my invention is the rovision of an improved electric fuse w ich shall function surely and efiectively under the various. current conditions imposed thereon, which shall not deteriorate in use and which shall be of low manufacturing resent invention. relates to electrical evices and morees ecially to high the expulsion Electric safety fuses generally comprise a fusible link of soft metal oralloy of limited current carrying capacity and. enclosed in a protective shell which serves also to contain the gases of fusion for a suflicient time so that the increased gas pressure incident to the blowing of the lmktherein may assist in the suppression of any are that tends to spring over the gap formed in the circuit upon the giving away of the fusible link.

When a fuse is subjected to a heavy short circuit, there is much dan er that the explosive. action of the volati e gases will disrupt the protective shell and this explosive action is more or less directly in proportion to the amount of metal volatilized.

When a fuse blows under a graduall augmented current, it may merely melt an drop away and inso. doing operate to draw an arc without substantial opposition across the gap thus formed in the circuit, so that al-' thou h the fusible link has blown up and 'va'nis ed the dangerous current continues to flow in the circuit.

I The hi her the potential of the dangerous current t e greater is the Likelihood that any failure of t e fuse to function will-be attended by serious consequences.

In carrying out my invention I reduce the length of the volatilizable metal link to the shortest compatible with the particular conditions and connect in series therewith a flexible length of relatively non-fusibleconductor to bridge the circuit interruptinggap and adapted to be bodil displaced upon the blowing of the fuse un er short circuit conditions, and, in order that an arc may not be drawn upon the giving awayof the fuse link under a gradual rise in overload, I provide ajspringso arranged as to withdraw the non-fusible conductor the instant the fusible element releases its hold. Other features of practical importance will be set forth hereinafter.

pulsion fuse; Rig.

One embodiment'of the invention is shown in the accompanying drawing, in which Fig. 1 is a side elevatlon of an expulsion fuse embodyin the invention mounted in its cut-out block; ig. 2 is an axial section of my ex- 3 is a plan view of the connection for upper end' of the fuse link; Fig. 4 is a in view of the connection for the lower en of the fuse, and Fig. cross-section thereof.

The fuse casin comprises an insulatin shell or tube 1 o horn fibre with a lengt' proportioned to the electric potential of the circuit to be protected and havin screwthreaded upon each end a contact gerrule 2 or 3 of cylindrical shape, one of which is closed or sealed and the other open or unsealed.

The fusible element consists of a link or strip 4 of zinc or other metal of low melting point and made very short so that the 5isa amount of metal volatilized upon blowing diametrically across'the upper end of the fibretube 1 and having arcuate or S-shaped spring ends 7 adapted to make contact with t e inner wall of the sealed contact ferrule 2. The lower end of the link 4 is folded and soldered about an end of a relatively infusible conductor 8 of fine copper wires which extends through the bore of the fibre tube 1 to a cap 9 having a disk-shaped head 10 and to which it is soldered:

The fusible link 4 is maintained under constant tension by a helical spring 11 thrusting against the end of the tube 1 at one end and at the other end against a sheet metal connection spider 12, through the center of which the cable 8 and its cap 9 are threaded with the head of the latter bearing against the lower side of the spider 12.

The connection spider 12 has three arms provided at their ends with cylindrical segments 1? adapted to bear against the inner wall of the contact ferrule '3. In order to insure good contact between the segments 13 and the ferrule while the fuse is intact and under tension, the spider arms; are dished by a slight curvature downward, so that with the tension of the spring 11 acting downward at their outer ends counter to the upward tension of the cable 8 acting at the center sion on the conductor 8.

In order to'protect the fibre tube 1 from the destructive action incident to the blowing of the fuse under. the action of a heavy short circuit, I provide thenearer or sealed contact ferrule 2 with a safety closure disk 14 having a crown flange 15 lightly soldered to the inner wall thereof so that it maybe displaced before the gas pressure exceeds the safety limit of the tube. -Wheneve ar the fuse link 4 blows under the action of a moderate short circuit with corresponding moderate gas pressure, the disk let-will remain sealed and cause the volatile gases to be expelled downwardly through the bore of the tube and thereby exert a blow-out efi'ect upon any are that may tend to'form as the conductor 8 is drawn outwardly by the recoil of the spring 11 through the openeend of'the casmg.

moisture of the air to deposit upon and oxidize the fusible element 4, I secure in an annular groove 16 in the inner wall of the lower terminal 3 a disk 17 of easily ruptured material, such as tin foil. which acts as a damper upon the circulation of air within the casing and at the same time is readily dis,- placed upon blowing of the fuse, while on account of its protected position within the terminal 3 it is not subject to injury or displacement in handling.

In use my fuse will be ordinarily mounted,'as shown in Fig. 1, in spring contact cli s 18 adapted to embrace the metal ferru es 2 and 3 and having cup-shaped bases 19 cemented to the tops of post insulators 20 and to which the ends 21 and 22 of the branch wire are attached.

While I have described and shown the best embodiment of the invention known to me, I do-not desire to be restricted thereto.

What Iclaim as new and desire to secure by Letters Patent of the United States, is:

1. An electric expulsion fuse comprising an elongated insulating shell with metallic end terminals, one of which terminals is re-' leasably sealed and the other unsealed, a short fusible link connected to said sealed terminal, a relatively non-fusible conductor In order to keep down the tendency of.

relatively non-fusible conductor connected to said link and extending longitudinally within said shell, a metallic spider connector between said unsealed terminal and the adjacent end of said non-fusible conductor and a spring operating normally to hold said metallic connector in contact with. said unsealed terminal and upon melting pf the fusible link to eject said metallic conductor from the shell.

3. An electric expulsion fuse comprising an elongated insulating shell with metallic end terminals, one of which terminals is sealed and the other unsealed, a fusible link within said shell and connected at one end to said sealed terminal, aspider connector attached through its center to the other end of said link and having springy cylindrical segments adapted to engage the inside of said unsealed terminal, and a helical spring thrusting against the said connector at points removed from the center thereof counter to the tension of said link.

4. An electric expulsion fuse comprising an elongated insulating shell with metallic end terminals, one of which terminals is sealed and the other unsealed, a fusible link within said shell and connected at one end to said sealed terminal, a sheet metal connector engageable through its center with the other end of said link and having curved arms provided with segmental ends adapted to engage the inside of said unsealed terminal,. and a helical spring disposed adjacent the inner wall of said unsealed terminal and thrusting outwardly against the outer ends of said curved arms and operating thereby normally to exert tension on said fusible link and to straighten said curved arms and effect binding cont-act upon the inner wall of said terminal.

In Witness whereof, I have hereunto set my hand this 10th day of July, 1925.

RICHARD R. MoGEE. 

